In July gunmen on motorcycles shot and killed Darioush Rezaeinejad, identified by Iranian news sites as an electronics student. He was identified by Western news sources as a specialist in the kind of high-voltage switch used to set off the explosions that trigger nuclear warheads.
In 2007 an Iranian nuclear scientist named Ardeshir Hassanpour died from what Iranian media said was accidental carbon monoxide poisoning from a faulty space heater in his home.
U.S.-based security analysis firm Statfor claimed Hassanpour was killed by Mossad, making him the first nuclear scientist killed in the campaign to stop Iran's nukes.
French web site Intelligence Online claimed Iranian security killed Hassanpour because he was planning to flee the country. None of the three versions of his death have been substantiated.
Today's attack makes the 32-year-old Rohan – who specialized in building systems to isolate volatile gasses during the refinement of nuclear material – the sixth nuclear scientist to be attacked and either the fourth or fifth to be killed.
"Assassinations, military threats and political pressures ... The enemy insists on the tactic of creating fear to stop Iran's peaceful nuclear activities," Fars quoted lawmaker Javad Jahangirzadeh as saying in reaction to the blast.
Israel is chief Iran nuke opponent, but it has plenty of company
The U.S., Israel, the U.K. and other Western powers have steadily increased political, diplomatic and economic pressure on Iran during the past two years in an effort to persuade it to drop what they call an effort to develop nuclear weapons.
Iran has insisted its nuclear program is a peaceful effort to develop nuclear power, not nuclear weapons.
Israel has been particularly adamant in its opposition to the Iranian nuclear program just as it has campaigned against the nuclear ambitions of other Middle Eastern countries through the U.N. and other diplomatic channels.